Charles Spencer Says His Sister Princess Diana Would Have Been the 'Best Grandmother Ever' to Prince George and Princess Charlotte

Since her death 20 years ago, one of the most outspoken advocates of Princess Diana‘s legacy has been her younger brother, Charles, 9th Earl Spencer. Her final resting place is on the grounds of Althorp, his current home and where the siblings’ shared their childhood home. He gave a powerful eulogy at her funeral, and continues to talk about his sister’s impact today.

Of all the tragic aspects of Princess Diana’s early death, one sticks out to her brother, Charles Spencer, is the fact that she’ll never get to meet her grandchildren, Prince George and Princess Charlotte.

“One of the great tragedies is that Diana would have been the best grandmother ever,” he said in in an interview featured in The Story of Diana, a two-part television event from PEOPLE and ABC.

Though Diana’s death is as tragic today as it was 20 years ago, Spencer said that a bright spot now is seeing memory live on through her two sons, Prince William and Prince Harry.

“I love seeing the sort of uncomplicated way that they deal with people, and put them at their ease,” he said. “It’s so easy to connect the dots between them and their mother.”

“What’s amazing to me is the passing of time,” he says. “Now William and Catherine are nearly the same age as Diana when she died.”

“I love the fact that there’s still such veneration inside her immediate family for what she was, and what she meant,” he continues. “I think that’s fantastic.”

A.G. Carrick/Diana Memorial Fund/Getty

In the days after her death, he was haunted by thoughts that he could have done something to save his sister from her tragic death.

“I was furious, I wasn’t just angry,” he said. “[I thought] what could I have done. But you always think, God, I wish I could’ve protected her. It was just…it was devastating.”

He adds: “I always felt…intensely protective towards her.”

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Spencer said he was inspired to open up about Diana because he wanted to help ensure her place in history.

“One of the reasons I wanted to talk now is because I think after 20 years, someone shifts from being a contemporary person to a person of history actually,” he says. “And Diana deserves a place in history.”

“I think that it’s important for people who are under 35, who probably won’t remember her at all, to remember that this is a special person,” he says. “Not just a beautiful one.”

For full PEOPLE coverage of the 20th anniversary of Princess Diana’s death:

•The Story of Diana, a two-part television event from PEOPLE and ABC, airs on ABC Aug. 9 and 10 at 9 p.m. E.T.